Fyson, U.S. Pat. No. 4,294,505, discloses bleach and bleach fix compositions and methods using a ferric complex of an alkyliminodiacetic acid. This invention comprises certain improvements over Fyson's compositions and methods. Thus, this invention comprises solutions and methods for bleaching metallic silver in photographic materials.
U.S. Pat. No. 5,061,608 discloses use of acetic, propionic, and succinic acid to inhibit bleach induced dye formation. In a preferred embodiment of this invention, bleach compositions of this invention are biodegradable, inasmuch as the alkyliminodiacetic acid portion of the compositions can be metabolized, at least to a significant extent, by microorganisms present in the environment. For biodegradability, methyliminodiacetic acid is a preferred ingredient of this invention.
This invention comprises in part use of pH levels not previously contemplated in the art, and it also provides the unexpected discovery of a synergistic bleaching interaction achieved at low iron and specified pH levels. Thus, the invention is considered to be a significant advance in the art. Moreover, bleaches provided by this invention achieve performance levels of current bleaches, using readily available materials that are well known. Consequently, this invention is readily adaptable by industry.